1. Field of the Invention
This invention relates to a battery unit mounting structure for fixing a battery unit as a power source for an electric vehicle to a vehicle body.
2. Description of the Related Art
An electric vehicle is expected to be mounted with a large battery unit to maximize its mileage. Therefore, some battery units may weigh more than, for example, 100 kgw. In order to fix one such heavy battery unit securely to side members of a vehicle body, it is essential to increase the strength of battery unit mounting portions of the side members. The side members are also referred to as side frames.
A battery support structure for fixing a battery unit to side members of a vehicle body is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 10-129277. In this battery support structure, reinforcing members are provided in the side member. Nuts are welded to the reinforcing members, individually. The battery unit is fixed to the side members by screwing bolts individually into the nuts from below the vehicle body and tightening the bolts.
The battery unit is expected to be supported in such a manner that its load is dispersed to a plurality of points on each side member. Therefore, the battery unit is fixed to battery unit mounting portions on a plurality of parts of each side member. In consideration of the required rigidity and relationships with their surrounding members, however, each side member is generally designed so that its cross-sectional shape varies along the longitudinal direction of the vehicle body.
The battery unit mounting portions are provided on a plurality of points in the longitudinal direction of each side member. These mounting portions vary in cross-sectional shape depending on their location. In some cases, therefore, the battery unit mounting portions cannot share reinforcing members of a common shape. Thus, it is necessary to manufacture a plurality of types of reinforcing members. In this case, many types of components must be used, so that the manufacturing cost is increased, and in addition, the components require laborious control or management.